The present invention relates generally to pilot cueing systems for aircraft. In particular, the present invention relates to tactile pilot cueing systems for the power levers, collectives, and throttles of aircraft.
Flying an aircraft is a complicated and demanding task. The pilot must be aware of many things going on at once. In particular, the pilot must be aware of the ever-changing operating conditions of the aircraft and all of its systems, such as the power systems and the flight control systems. The pilot must know not only the current state of these systems, but their operational limits as well. To do this, the pilot must scan multiple engine and torque gauges to determine operating conditions and limitations. Failure by the pilot to carefully monitor these systems can lead to serious problems. The following are examples of problems that can result from the pilot failing to monitor the operational parameters of the aircraft: (1) increased operational and maintenance costs as a result of inadvertent power commands in excess of torque or temperature limits; and (2) unpredictable vertical axis control as a result of a power lever deadzone during operations with limited engine power, such as one-engine-inoperative (OEI) flight conditions.
Some aircraft use mechanical springs to provide a tactile cue to the pilot through the control levers to indicate that the operational limits of the aircraft are being approached. Such mechanical springs engage at set predetermined levels and supply a predetermined amount of resisting force to the controls. These preset levels cannot be changed once the springs are installed. Furthermore, these mechanical springs add weight to the aircraft.
There is a need for a power lever tactile cueing system for an aircraft for which the magnitude of the tactile force can be altered depending upon certain dynamic conditions of the aircraft, and for which mechanical springs are not required.
Therefore, it is an object of the present invention to provide a power lever tactile cueing system for an aircraft for which the magnitude of the tactile force can be altered depending upon certain dynamic conditions of the aircraft, and for which mechanical springs are not required.
The above objects are achieved by providing a power lever tactile cueing system in which mechanical springs are replaced by computer controlled software, a variable friction magnetic particle clutch, and an electric trim motor. In the preferred embodiment of the present invention, the following tactile alerts are employed: a power lever softstop and a power lever backdrive. These tactile alerts provide a spring-like tactile cue when power commands reach a predetermined operating limit. The backdrive commands cause the power lever to be trimmed down at a variable rate based upon the operating conditions of the aircraft and the engines. The tactile cue remains active until the aircraft and engine conditions no longer exceed the operational limits. The pilot can deliberately override the tactile cue in an emergency situation.
The present invention provides the following advantages: (1) reduces pilot workload by allowing the pilot to determine operating limits without continually monitoring multiple engine and drive system gauges in the cockpit; (2) improves flight safety by reducing the likelihood of exceeding engine and drive system operating limits; (3) improves operational costs by reducing the likelihood of engine and drive system overhauls resulting from inadvertent exceedances of operational limits; (4) improves flight safety by allowing the pilot to override normal operational limits, but not allowing the pilot to override structural design static limits; (5) improves aircraft performance during maximum gross weight vertical takeoffs by allowing the pilot to set power to 100% of the operating limit without continually monitoring multiple engine and drive system gauges; (6) reduces pilot workload following an engine failure by automatically eliminating control deadzone in the power lever when operating on an engine limit; (7) provides a low-weight implementation of the tactile cue by using the same equipment required for autopilot operation; (8) provides an immediate tactile cue to the pilot that the aircraft has become power-limited as a result of a propulsion system malfunction; (9) eliminates the requirement for the pilot to manually modulate the power lever when power limits change as a function of flight condition; and (10) reduces weight by eliminating the need for mechanical springs.
The above objects and advantages, as well as others, will be evident from the following detailed description of the present invention.